Eleven manufacturers holding licenses to produce Allergenic Extracts in the US have been approved to manufacture and sell standardized Extract of Dermatophagoides pteronyssinus mite. Twelve are approved to manufacture and distribute extract of Dermatophagoides farinae mite. The Laboratory continues to evaluate mite extracts produced from mites that have been raised under different culture conditions, to attempt to detect possible compositional or quantitative differences in these products. Tests to evaluate these extracts include immunoblotting, RAST inhibition, assays for total protein, and clinical testing.